Depth of the Kindness Hormone Appears to Know Some Bounds

By NICHOLAS WADE

Yes, you knew there had to be a catch. As oxytocin comes into sharper focus, its social radius of action turns out to have definite limits. The love and trust it promotes are not toward the world in general, just toward a person’s in-group. Oxytocin turns out to be the hormone of the clan, not of universal brotherhood. Psychologists trying to specify its role have now concluded it is the agent of ethnocentrism.

A principal author of the new take on oxytocin is Carsten K. W. De Dreu, a psychologist at the University of Amsterdam. Reading the growing literature on the warm and cuddly effects of oxytocin, he decided on evolutionary principles that no one who placed unbounded trust in others could survive. Thus there must be limits on oxytocin’s ability to induce trust, he assumed, and he set out to define them.

In a report published last year in Science, based on experiments in which subjects distributed money, he and colleagues showed that doses of oxytocin made people more likely to favor the in-group at the expense of an out-group. With a new set of experiments in Tuesday’s issue of the Proceedings of the National Academy of Sciences, he has extended his study to ethnic attitudes, using Muslims and Germans as the out-groups for his subjects, Dutch college students.

These nationalities were chosen because of a 2005 poll that showed that 51 percent of Dutch citizens held unfavorable opinions about Muslims, and other surveys that Germans, although seen by the Dutch as less threatening, were nevertheless regarded as “aggressive, arrogant and cold.”

Well-socialized Dutch students might be unlikely to say anything derogatory about other groups. So one set of Dr. De Dreu’s experiments tapped into the unconscious mind by asking subjects simply to press a key when shown a pair of words. One word had either positive or negative connotations. The other was either a common Dutch first name like Peter, or an out-group name, like Markus or Helmut for the Germans, and Ahmad or Youssef for the Muslims.

What is measured is the length of time a subject takes to press a key. If both words have the same emotional value, the subject will press the key more quickly than if the emotional overtones conflict and the mind takes longer to reach a decision. Subjects who had sniffed a dose of oxytocin 40 minutes earlier were significantly more likely to favor the in-group, Dr. De Dreu reported.

In another set of experiments the Dutch students were given standard moral dilemmas in which a choice must be made about whether to help a person onto an overloaded lifeboat, thereby drowning the five already there, or saving five people in the path of a train by throwing a bystander onto the tracks.

In Dr. De Dreu’s experiments, the five people who might be saved were nameless, but the sacrificial victim had either a Dutch or a Muslim name. Subjects who had taken oxytocin were far more likely to sacrifice the Muhammads than the Maartens.

Despite the limitation on oxytocin’s social reach, its effect seems to be achieved more through inducing feelings of loyalty to the in-group than by fomenting hatred of the out-group. The Dutch researchers found some evidence that it enhances negative feelings, but this was not conclusive. “Oxytocin creates intergroup bias primarily because it motivates in-group favoritism and because it motivates out-group derogation,” they write.

Dr. De Dreu plans to investigate whether oxytocin mediates other social behaviors that evolutionary psychologists think evolved in early human groups. Besides loyalty to one’s own group, there would also have been survival advantages in rewarding cooperation and punishing deviants. Oxytocin, if it underlies these behaviors too, would perhaps have helped ancient populations set norms of behavior.

Early religions were also involved in establishing group cohesion and penalizing offenders. Could oxytocin be involved in the social aspects of the religious experience? Dr. De Dreu sees oxytocin’s effects as being very general, and no more likely to be associated with the religious experience than with soccer hooliganism. “When people get together with others who share their values, that drives up the level of oxytocin,” he said.

For military commanders, nothing is more important than the group cohesion of their soldiers, for which oxytocin might now seem the ideal prescription. But this assumption is a bridge too far, Dr. De Dreu said, given that his findings are based only on lab experiments.

What does it mean that a chemical basis for ethnocentrism is embedded in the human brain? “In the ancestral environment it was very important for people to detect in others whether they had a long-term commitment to the group,” Dr. De Dreu said. “Ethnocentrism is a very basic part of humans, and it’s not something we can change by education. That doesn’t mean that the negative aspects of it should be taken for granted.”

Bruno B. Averbeck, an expert on the brain’s emotional processes at the National Institute of Mental Health, said that the effects of oxytocin described in Dr. De Dreu’s report were interesting but not necessarily dominant. The brain weighs emotional attitudes like those prompted by oxytocin against information available to the conscious mind. If there is no cognitive information in a situation in which a decision has to be made, like whether to trust a stranger about whom nothing is known, the brain will go with the emotional advice from its oxytocin system, but otherwise rational data will be weighed against the influence from oxytocin and may well override it, Dr. Averbeck said.

Dr. Averbeck said he was amazed that a substance like oxytocin can affect such a high-level human behavior. “It’s really surprising to me that this neurotransmitter can so specifically affect these social behaviors,” he said.